Chip brags to his new playmate that his genius brother Robbie can fix almost anything. Soon Robbie is repairing a Grand Piano and has five minutes to have it fixed before the boy's mother comes in and wants to practise a new tune on it.

Unaware of each other's problems, Steve and Robbie engage in what seem to be widely varied projects. Robbie is trying to construct a race kart and Steve is in a rush to help a missile manufacturer get his project off the launch pad in a race to beat a rival company.